1. Field of the Invention
The present invention relates to a liquid crystal display device.
2. Discussion of the Related Art
Until recently, display devices have typically used cathode-ray tubes (CRTs). Presently, many efforts and studies are being made to develop various types of flat panel displays, such as liquid crystal display (LCD) devices, plasma display panels (PDPs), field emission displays, and electro-luminescence displays (ELDs), as a substitute for CRTs. Of these flat panel displays, LCD devices have many advantages, such as high resolution, light weight, thin profile, compact size, and low voltage power supply requirements.
In general, an LCD device includes two substrates that are spaced apart and face each other with a liquid crystal material interposed between the two substrates. The two substrates include electrodes that face each other such that a voltage applied between the electrodes induces an electric field across the liquid crystal material. Alignment of the liquid crystal molecules in the liquid crystal material changes in accordance with the intensity of the induced electric field into the direction of the induced electric field, thereby changing the light transmissivity of the LCD device. Thus, the LCD device displays images by varying the intensity of the induced electric field.
FIG. 1 is a perspective view illustrating an LCD device according to the related art.
Referring to FIG. 1, the LCD device 1 includes an array substrate 10, a color filter substrate 20 and a liquid crystal layer 30 between the array substrate 10 and the color filter substrate 20.
The array substrate 10 includes gate and data lines 14 and 16 crossing each other on a first e12 to define a pixel region P. A thin film transistor Tr is formed at a crossing portion of the gate and data lines 14 and 16. A pixel electrode 18 in the pixel region P is connected to the thin film transistor Tr.
The color filter substrate 20 includes a black matrix 25 on a second substrate 22 and corresponding to the gate and data lines 14 and 16 and the thin film transistor Tr. A color filter layer 26 corresponds to the pixel region P. The color filter layer includes red (R), green (G) and blue (B) color filter patterns 26a, 26b and 26c corresponding to the respective pixel regions P. A common electrode 28 is formed on the black matrix 25 and the color filter layer 26.
Although not shown in the drawings, spacers are located between the array substrate 10 and the color filter substrate 20 to maintain a cell gap therebetween and spaced apart from one another. The spacer is a ball spacer or patterned spacer. Further, a sealant is located along peripheral portions of the array substrate 10 and the color filter substrate 20 to prevent leakage of the liquid crystal layer 30. Further, polarizing plates are formed on outer surfaces of the array substrate 10 and the color filter substrate 20, respectively. A backlight unit is below the array substrate 10 to supply light.
When a gate signal is supplied to the gate line 14, the thin film transistor Tr is turned on and a data signal is supplied through the data line 16 to the pixel electrode 18. Accordingly, an electric field is induced between the pixel electrode 16 and the common electrode 28, and images are displayed through the LCD device 1.
FIG. 2 is a plan view illustrating an LCD device including a patterned spacer according to the related art, FIG. 3 is a view illustrating a black matrix configuration designed for the LCD device according to the related art, and FIG. 4 is a view illustrating a black matrix configuration actually formed for the LCD device according to the related art.
Referring to FIG. 2, the LCD device 35 includes an array substrate 40 in which gate and data lines 43 and 55 cross each other to define a pixel region P. A pixel electrode 67 is formed in the pixel region P and connected to a thin film transistor Tr.
The color filter substrate includes a black matrix 75 having openings corresponding to respective pixel regions P, red (R), green (G) and blue (B) color filter patterns filling the respective openings of the black matrix 75, and a common electrode covering the black matrix 75 and the color filter patterns.
Patterned spacers 83 are formed over the common electrode and overlap the black matrix 75. The patterned spacers 83 are spaced apart from one another and each have a cylindrical shape. The patterned spacers 83 function to maintain a cell gap between the array substrate 40 and the color filter substrate.
The black matrix 75 corresponding to the patterned spacer 83 should have the same shape as the patterned spacer 83 to prevent light leakage around the patterned spacer 83.
The patterned spacer 83 is generally designed to have a diameter of about 8 μm (micrometers) to about 13 μm to maintain the cell gap without defect of its falling down due to an external pressure.
However, a rubbing of an alignment layer is not made well in the region, where the patterned spacer 83 is formed, because of large step. Accordingly, abnormal rubbing occurs in a region of a diameter of about 10 μm to about 12 μm greater than the diameter of the black matrix 75 with respect to a center of the black matrix 75. Accordingly, light leakage occurs in a region LOA up to about 5 μm to about 6 μm from a circumference of the patterned spacer 83.
To block the light leakage region LOA, the black matrix 75 extends up to about 5 μm to about 6 μm from the circumference of the patterned spacer 83.
Referring to FIG. 3, the black matrix 75 is designed to be wider than that of the patterned spacer 83 considering the light leakage region LOA. However, referring to FIG. 4, because of light diffraction in forming the black matrix 75, the black matrix 75 actually formed has a shape that is not outward round as the patterned spacer 83 but inward round.
As such, the black matrix 75 is not formed as designed, and the light leakage region LOA is not fully blocked thus. Accordingly, light leakage occurs around the black matrix 75.
To prevent this problem, the black matrix 75 may be formed to have a greater width. However, this causes the black matrix 75 to more block the pixel region P, and aperture ration is reduced.